The present invention generally refers to a safety switch, and in particular to a safety switch for effecting a shutdown of a current supply, for example when removing a protective cover from an appliance, a machine or the like or when opening an access door or the like.
Safety switches of this type conventionally include a housing in which a contact-bearing tappet is movably supported and acted upon by a switch wheel which is rotatably supported in the housing and turned by an actuator of adapted configuration for movement between an initial position and a switching direction. The housing has openings on two sides for insertion by the actuator, with the switch wheel including spring-biased locking members on both sides for locking a rotational movement of the switch wheel. The locking members are movable by the actuator in opposition to the spring force into a position releasing the switch wheel.
In order to meet safety demands, measures must be undertaken to prevent easy copying of the actuator for activating the switch through unauthorized persons or untimely or unintentional activation by an operator. Since upon manufacture of such safety switches their actual site and positioning of installation are generally not known, the safety switches are designed to allow activation by the actuator e.g. from two sides in order to minimize the required number of types of such safety switches and to render them consumer-friendly.
German Patent Nos. DE 31 00 862 C2 and DE 33 30 109 C2 disclose safety switches of this type in which the switch wheel is essentially split into two parts. A central part cooperates with the contacts-carrying tappet while lateral parts of the switch wheel are moved parallel to the pivot axis of the switch wheel in opposition of return springs by an actuator which is inserted through openings on two different housing sides in order to disengage stop members on the tappet from locking surfaces on the movable parts of the switch wheels. Thus, the locking members are formed by elements of the split switch wheel. Upon insertion of the actuator in one opening to activate the safety switch, the switch wheel is moved from a central position in one rotational direction while insertion of the actuator in the other opening results in a movement of the switch wheel in the other rotational direction. This means that the switch wheel is moved in different directions of rotation depending on which opening is used for the actuator.
Since the switch wheel itself assumes locking functions and, moreover, operates in two different directions of rotation depending on the insertion of the actuator into one or the other opening, the switch wheel requires many degrees of freedom. Evidently, the safety mechanism against unauthorized use or untimely actuation needs improvement. Also, the locking function is effected through locking with the movable, resiliently mounted tappet. This fact and the fact that the switch wheel is turned from a central position in either direction of rotation involves certain factors of uncertainty for the safety switch, in particular when resorting to force to activate the safety switch.
German utility model DE-GM 76 27 192 describes a further safety switch, with a housing provided with openings for allowing actuation in two different directions. When changing the direction of rotation, the entire switching mechanism must be dismantled and reassembled in the other position. Moreover, the overall construction is relatively simple and dimensioned for many degrees of freedom so that the manipulation safety needs improvement.
In accordance with a further known safety switch (WO 91/10247) which includes a switch wheel which cooperates with the tappet, with locking members being arranged laterally of the switch wheel. The locking members are movable parallel to the pivot axis of the switch wheel and are lockingly engageable in the switch wheel. Activation of the safety switch is evidently possible only in one direction. The actuator and both lateral locking members are of simple configuration so that the manipulation safety needs also improvement.